Not a wise decision. It is in PTI's own interest to hang the issue of Panama around the neck of Nawaz Sharif during next elections. Therefore, it should try to prolong the issue. If a commission is established, it may take up to a year or more to reach a conclusion. This will take us very close to next elections with PMLN still reeling under the burden of Panama. This would be a win-win for PTI no matter what the commission finds out.
On the other hand if Supreme Court makes a decision right now in favour of Nawaz Sharif and exonerates him, then PMLN will get a boost and PTI will have to find a new issue for the next elections. Even if the court decides something which is damaging to PMLN, still they'll have ample time before next elections to do damage control.
So this decision by Imran Khan seems to be an emotional one rather than a well thought out one.